Fascinating Fasciation

Chances are, you have seen fasciation on your own garden plants and maybe thought ‘how weird’ and did not think much more about it. Fasciation is a mutation in a plant’s growth habit, which causes the plant to grow flattened, elongated shoots and flower heads that look like many stems compressed together. I recently came across an Aeonium arboreum on Alcatraz that has a branch of flattened growth with many dwarf rosettes growing along the top of the flattened stem.

The flattened stem of affected stem compared to the normal round stem of the aeonium. Photo by Shelagh Fritz

So why does this mutation happen? Geoff Stein submittedan article for the website, Dave’s Gardens, and describes various theories but the precise cause is unknown. A bacterial, fungal or viral infection may cause some genetic mutation and a phytoplasma (a mix of a bacteria and a virus) has been proven to cause the mutation in some species. Of course, chemical and physical trauma are possibilities, though usually that sort of trauma damages the meristem (growth center) in such a way that the plant simply begins to divide, resulting in ‘ordinary’ branching or multiple heads. Perhaps radiation from the sun is another possible mutation cause. Some plants seem more prone to this mutation at various seasons, so temperature, humidity or heat may have some influence. Some nutritional deficiencies have been known to lead to cresting mutations (e.g., Zinc deficiency) as well. Sometimes mutations can occur spontaneously, just a chromosomal malfunction.

Mutated leaves of this aeonium are smaller than the normal rosette of leaves. Photo by Shelagh Fritz

These mutations are not passed along through seed, but, as Stein notes, there has to be some sort of genetic tendency for these mutations to occur as many species form fasciations fairly commonly while others have never been found to do so. Succulents and cacti tend to be fasciated quite often. For the number of succulents on the island though, this is the first time we have seen this growth.

Fasciated growth is not uncommon in other plants – forsythia being one of the more common. Recently, a Golden Gate National Parks Conservancy field staff noticed the mutation happening in poison oak!

Cuttings can be done of the mutated growth and a quick search on websites, show that these mutations can be highly desired. Perhaps we will start a fascinating fasciation garden?